APRAC3 contains two recent modifications to previous versions: (1) The emission factor computation methodology has been revised to reflect recent updates, and that portion of the code that performs emissions computations has been separated from the other portions of the model to facilitate incorporation of future emission factor methodology updates, and (2) Treating traffic links in the primary network with low vehicle miles traveled as area sources. Two local source models are available: (1) Treating pollutant behavior in a street canyon, and (2) Treating vehicle and pollutant effects at a signalized intersection. A preprocessor PREMOD2 is associated with this model.